Any business manager or executive responsible for operating transformers should be acutely aware of the possible consequences if they suffer a breakdown. The potential impact on production commitments and financial performance is enough to give people nightmares.
Bushings are one of the most important transformer components to monitor because their failure can result in fire and even explosions. Research cited in a study by Western Power and ABB claims high-voltage bushings contribute to about 30 per cent of all fires and explosions associated with transformer breakdowns.
Transformers are commonly operated by manufacturers, power generation and transmission companies, as well as mines, smelters, steel mills, pulp and paper plants and chemical plants. So how do people reduce the risk of bushing failure in a business?
FM Global insures 1,800 power-generation facilities worldwide, including about 20 per cent of Australia’s – and seven per cent of the world’s – generation capacity. This insurance coverage includes more than 100,000 transformers.
About two thirds of these transformers are in manufacturing facilities, including steel mills, pulp and paper plants, chemical plants and general manufacturing. FM Global manufacturing clients’ loss experience has shown that in the past 10 years, bushing failures accounted for just over a third (34 per cent) of transformer failures and a fifth (20 per cent) of transformer losses.
FM Global uses its extensive track record and specialist insurance model to help reduce bushing failure risk. Along the way FM Global has uncovered some key trends and best practices that can help manufacturers reduce bushing-related downtime and loss.
Globally during the past decade, FM Global’s clients in the power generation sector have experienced transformer losses of about $1.3 billion due to more than 550 transformer failures. Bushings accounted for eight per cent of failures and 12 per cent of losses. After comparing its numbers against research by other specialist organisations, FM Global found these numbers ring true beyond its client base.
To help clients reduce risk, FM Global wanted to get a better idea of what causes bushing failure. The company started by looking for any correlation between bushing age and failure. One operator experienced the misfortune of bushing failure after five years of use with a cost of over US$15 million. At the other end of the scale, another operator experienced a failure after 63 years of use that only resulted in a small cost to the business.
Most bushing failures occur between 10 and 30 years of use, but FM Global’s research was unable to draw a definitive correlation between bushing failure and age. Although there’s no hard and fast rule, there’s good reason to replace bushings at least once in a transformer’s life.
Is there an ideal testing regime to minimise risk? FM Global has seen many transformer owners experience bushing failures caused by poor test procedures or where equipment is improperly returned to service after an offline test. FM Global believes that it makes sense to only move to offline testing or more intrusive testing if the results of online monitoring suggest that there’s a need for more testing.
Online monitoring and contingency planning help operators to understand when a piece of equipment will likely fail and implement remediation steps. FM Global recommends that transformer operators adopt online monitoring to help minimise the risk of bushing failures.
Online monitoring and diagnostics of bushings can include visual inspections by experts, thermographic surveys, acoustic, corona and partial discharge measurements as well as permanently installed transformer condition monitoring devices. As part of online monitoring, FM Global feels that it’s essential for operators to adopt the benchmark International Council on Large Electric Systems model of asset maintenance.
To further minimise disruption in the event of a problem, FM Global also recommends that transformer operators keep spare bushings maintained in good condition onsite.
FM Global believes that the majority of losses are preventable. The company wants to work with clients that share this philosophy and demonstrate commitment to it through risk management practices.
Over the years, FM Global has developed powerful analytics tools that predict when equipment or locations are likely to experience losses. The company then makes recommendations to minimise the risk of these losses happening.
The devil is in the detail. Bushings are a fraction of the transformer’s cost, but their failure can result in the loss of not just the transformer but also peripheral damage to other equipment in a manufacturing plant and lost revenue.
FM Global believes that the price of a failure is too high to ignore. There’s great value in manufacturers making their business more resilient and less exposed to nasty surprises.